The C-terminal disordered loop domain of Apc8 unlocks APC/C mitotic activation

Cell Rep. 2024 Jun 25;43(6):114262. doi: 10.1016/j.celrep.2024.114262. Epub 2024 May 21.

Abstract

The anaphase-promoting complex/cyclosome (APC/C) is a critical and tightly regulated E3 ligase that orchestrates the cellular life cycle by controlling the degradation of cell cycle regulators. An intriguing feature of this complex is an autoinhibition mechanism: an intrinsically disordered loop domain, Apc1-300L, blocks Cdc20 coactivator binding, yet phosphorylation of Apc1-300L counteracts this autoinhibition. Many such disordered loops within APC/C remain unexplored. Our systematic analysis of loop-deficient APC/C mutants uncovered a pivotal role for Apc8's C-terminal loop (Apc8-L) in mitotic activation. Apc8-L directly recruits the CDK adaptor protein, Xe-p9/Cks2, positioning the Xe-p9-CDK-CycB complex near Apc1-300L. This stimulates the phosphorylation and removal of Apc1-300L, prompting the formation of active APC/CCdc20. Strikingly, without both Apc8-L and Apc3-L, the APC/C is rendered inactive during mitosis, highlighting Apc8-L's synergistic role with other loops and kinases. This study broadens our understanding of the intricate dynamics in APC/C regulation and provides insights on the regulation of macromolecular complexes.

Keywords: APC/C; CDK; CP: Molecular biology; Cdc20; Cks; cell cycle; crosslinking mass spectrometry; intrinsically disordered regions; phosphorylation; proteolysis; ubiquitin ligase.

MeSH terms

  • Anaphase-Promoting Complex-Cyclosome / metabolism
  • Animals
  • Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome / metabolism
  • Cdc20 Proteins / metabolism
  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Female
  • Mitosis*
  • Phosphorylation
  • Protein Binding
  • Protein Domains
  • Xenopus laevis

Substances

  • Anaphase-Promoting Complex-Cyclosome
  • Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome
  • Cdc20 Proteins
  • Cell Cycle Proteins